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Summary: A polyhedral microporous carbon derived from metal‐organic frameworks (ZIF‐8) could present good property for sulfur loading and trapping. A melting‐evaporation route was adopted to synthesize two sulfur/microporous carbon (S/MC) composites, of which sulfur content is controllable, and ether‐based or ester‐based electrolytes were used to evaluate the synthesized composites for the lithium sulfur batteries. According to electrochemical results, the S/MC composite with 65.2 wt% S in the ether‐based electrolyte exhibited optimized performance as compared with the composite with 65.2 wt% S in the ester‐based electrolyte, as well as the composite with 58.6 wt% S in the two kinds of electrolytes. For the S/MC composite with 65.2 wt% S in ether‐based electrolyte, the initial discharge capacity could reach up to 1505.9 mAh g−1 and the reversible capacity could be 833.3 mAh g−1 after 40 cycles at 0.1 C. Furthermore, while being respectively evaluated at 0.5, 1.0, and 2.0 C, the discharge capacities could still maintain at 544, 493 and 354 mAh g−1 after 300, 500, and 800 cycles, demonstrating appreciable cyclic reversibility and rate capability. [ABSTRACT FROM AUTHOR]

The lithium-sulfur flow battery (LSFB) is a new addition to the rechargeable lithium flow batteries (LFBs) where sulfur or a sulfur compound is used as the cathode material against the lithium anode. We report here our evaluation of an organic sulfide - dimethyl trisulfide (DMTS), as 1) a catholyte of a LFB and 2) a multi-electron redox mediator for discharging and charging a solid sulfur cathode without any conductive additives. The latter configuration is also known as the redox-targeting lithium-sulfur flow battery (RTLSFB). The LFB provides an initial discharge capacity of 131.5 mAh g −1 DMTS (1.66 A h L −1 ), which decreases to 59 mAh g −1 DMTS (0.75 A h L −1 ) after 40 cycles. The RTLSFB delivers a significantly higher application performance - initial discharge capacity of 1225.3 mAh g −1 sulfur (3.83 A h L −1 ), for which 1030.9 mAh g −1 sulfur (3.23 A h L −1 ) is still available after 40 cycles. The significant increase in the discharge and charge duration of the LFB after sulfur addition indicates that DMTS is better used as a redox mediator in a RTLSFB than as a catholyte in a LFB. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoN-Mo 2 N heterostructure is synthesized by nitriding the CoMoO 4 nanorods; • CoN-Mo 2 N heterostructure has strong adsorption/bidirectional catalytic capacity for polysulfides; • Li-S cells assembled with CoN-Mo 2 N modified separators show excellent electrochemical performance. A single functional material can hardly simultaneously overcome the problems of poor conductivity of active sulfur, shuttle effect and slow redox reaction kinetics of lithium polysulfides (LiPSs) in rechargeable lithium-sulfur batteries. Herein, a multi-functional CoN-Mo 2 N heterostructure nanorods with excellent adsorption capability and bidirectional catalytic ability is introduced. It is found that the CoN-Mo 2 N heterostructure has a significant interaction with LiPSs, and its chemical affinity can promote the adsorption of LiPSs; The Li 2 S nucleation and electrochemical testing results show that the CoN-Mo 2 N heterostructure can promote the uniform nucleation and rapid growth of Li 2 S, where CoN tends to promote the oxidation reaction kinetics, and Mo 2 N promotes the reduction reaction kinetics. The assembled Li-S cells with CoN-Mo 2 N modified separators can deliver outstanding rate performance and long-cycling stability, with a high initial reversible discharge capacity of 1605.8 mAh g−1 at 0.1C, and capacity decay rate per cycle of 0.198 % after 200 cycles at 0.2C. [ABSTRACT FROM AUTHOR]

Since the separator commonly used in lithium sulfur batteries has a large pore size and the adsorption effect of polyolefin based materials on soluble polysulfides is not obvious, the research on the modification of separator has aroused great interest. In this paper, the effects of different sizes of CoMoO 4 nanorods as functional coating materials on the performance of lithium-sulfur batteries were investigated. The results prove that there is a strong affinity between the Co-O-Mo polar bond of CoMoO 4 and LiPSs, which can enhance the chemisorption of LiPSs; Moreover, compared with CoMoO 4 -12, CoMoO 4 -24 nanorods with smaller particle size can increase the contact area and reactive sites with electrolyte, and the electrolyte penetration is promoted in the CoMoO 4 -24 coated separator, and the rapid transformation of LiPSs during charge and discharge is realized. Therefore, the Li-S battery assembled with CoMoO 4 -24 coated separator can deliver an initial capacity of 1018.5 mAh g−1 at 0.2C and a capacity retention of 745.5 mAh g−1 after 200 cycles, higher than the cells assembled with CoMoO 4 -12 coated separator and blank separator, exhibiting more remarkable electrochemical performance. • The CoMoO 4 nanorods were synthesized by hydrothermal method and subsequent thermal annealing method. • The CoMoO 4 nanorods were used as adsorption/catalytic medium to fabricate functional separator. • Li-S battery assembled with CoMoO 4 -24 coated separator shows better electrochemical performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoSe@NC nanofiber membrane was synthesized by electrospinning and thermal annealing method. • CoSe nanoparticles have strong adsorption and catalytic capability for polysulfides. • Li-S battery with CoSe@NC nanofiber membrane as interlayer shows excellent electrochemical performance. Lithium sulfur (Li-S) batteries have attracted tremendous attention due to their low cost and high theoretical capacity. However, the serious polysulfides shuttle and slow redox reaction kinetics hinder their large-scale commercial applications. Various attempts have been made to solve the problems. Herein, a CoSe@NC nanofiber membrane was prepared by electrospinning method and used as independent functional interlayer for the Li-S batteries. The visualized adsorption experiments show that the CoSe@NC nanofiber exhibits strong adsorption capability for polysulfides; In addition, CoSe nanoparticles with strong catalytic activity can accelerate the conversion of polysulfides. The adsorption-catalysis synergy of CoSe@NC can therefore effectively enhance the rate performance and cycling stability of Li-S batteries. The cell assembled with CoSe@NC functional interlayer delivers a high initial reversible discharge capacity of 1317 mAh g−1 at 0.1 C rate. After 200 cycles at 1.0 C, the capacity decay rate is only 0.16% per cycle. This work provides a feasible way to promote the electrochemical performance of Li-S batteries [ABSTRACT FROM AUTHOR]